drm/modes: Make sure to parse valid rotation value from cmdline

A rotation value should have exactly one rotation angle.
At the moment there is no validation for this when parsing video=
parameters from the command line. This causes problems later on
when we try to combine the command line rotation with the panel
orientation.

To make sure that we generate a valid rotation value:
  - Set DRM_MODE_ROTATE_0 by default (if no rotate= option is set)
  - Validate that there is exactly one rotation angle set
    (i.e. specifying the rotate= option multiple times is invalid)

Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20200117153429.54700-2-stephan@gerhold.net

1 files changed, 7 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
index 10336b144c72..d4d64518e11b 100644
--- a/drivers/gpu/drm/drm_modes.c
+++ b/drivers/gpu/drm/drm_modes.c
@@ -1698,6 +1698,13 @@ static int drm_mode_parse_cmdline_options(const char *str,
 	if (rotation && freestanding)
 		return -EINVAL;
 
+	if (!(rotation & DRM_MODE_ROTATE_MASK))
+		rotation |= DRM_MODE_ROTATE_0;
+
+	/* Make sure there is exactly one rotation defined */
+	if (!is_power_of_2(rotation & DRM_MODE_ROTATE_MASK))
+		return -EINVAL;
+
 	mode->rotation_reflection = rotation;
 
 	return 0;